"The Mowercycle" a microcar road legal trike

So I have enough parts together that it's time to start a project thread. I am going to build a three wheel mowercycle / microcar.

Backstory Begins

The other day I was driving to work, and I really looked at my car. Literally all I use this car for is driving to and from work. I have space for 5 people, and thousands of pounds of metal, and I'm burning lots of gas just to haul all this wasted space back and forth to work. It just seems unnecessary. Also, this car is starting to fall apart. It's loud, the mpgs are slowly going down, the brakes are dragging, and I'm tired of it. My commute is 25 miles of back roads, so I can't like, ride a bike or anything, I need speed.

For some reason I got it in my head that instead of fixing my current car, I would rather build a new one, or at least try. After all, I always wanted to build my own car, and free myself from the problems of "oh, this part is rare and expensive, even though you can buy a part that does the same thing in a different car for $20" and "Oh, you don't have a car lift and $1000 worth of tools? Enjoy spending all day with your back in the dirt and bugs trying to get rusty bolts loose." I hate working on anything bigger than say a golf cart.

I can hear it now. "Why don't you get a motorcycle?" you say. Well, I rode a motorcycle in college. In the winter. Until the first snow. It sucked. It's also a little too dangerous for my taste now that I have a family. My commute is all back roads. I don't encounter much traffic, but what I do have to worry about is deer. Also, I dont want to crash because I hit some wet leaves and lose traction. Therefore I would like to be able to have 3 wheels, a bumper, a real seat, and a seatbelt to keep me from having an intimate moment with the asphalt if I ever engage ruminants in high speed melee combat.

I also want other things, like maybe a windshield someday, and heat. Also, I need it to be road legal. This means I practically MUST have three wheels. Once you add that fourth wheel, suddenly it's a car and needs a bunch of extra equipment, like windshield wipers and washers, a parking brake, safety glass windshield, and a bright light dash indicator. A three wheeled vehicle just needs brakes, lights, mirrors, and a horn. Oh, and you need DOT approved tires. That's actually been one of the hardest / most expensive parts.

Obviously I'm not going to get a fully enclosed microcar in my first build. But if I build with that goal in mind, I can use everything I learn in a future project or projects. People build stuff like this in their garage all the time, so it's very possible.

Why am I doing one wheel in the front, and not a reverse trike? Aren't reverse trikes better in pretty much every way? Well, not entirely. On paper, they are absolutely better as far as handling and stability goes. However in my situation, it just didn't work out that way. Two wheels in the front significantly increases complexity. Suddenly you have all sorts of steering and suspension geometry to deal with. With one wheel in the front, you just need to worry about fork angle and trail. Also, in my case, it worked out much cheaper. Trying to round up two wheels that you can buy DOT tires for, hubs, brakes, and have all of it be compatible was looking to be super expensive. Not to mention suspension. Cost is also one of the reasons I didn't consider a motorcycle engine. Used ones are super expensive in my area right now, plus I would've had to find or build a differential. Lacking the stability of a reverse trike, I'll sadly be forced to not speed around curves. Truly a great sacrifice.

As far as I go myself, I'm an engineer with lots of diy, mechanical, and electronics experience. My youtube channel has a sampling of previous projects. I've got a small flux core welder, 3d printer, and random hand tools. Oh and I've got a large HAAS CNC at work that's basically my personal pet. Especially since it sits idle most of the time and I'm the only one who ever uses it.

Backstory Ends

Okay, now that the backstory is over, we can move on to the project itself. We have our constraints:
Three wheels, with the ability to get DOT tires.
High speed, at least 45mph
super strong racing design not required, high speed but gentle use. No donuts, burnouts, or wheelies will be found here.
Differential, brakes on front and rear are legal requirements.
Lights and horn.
Cheap, I can't invest much until I have something I can point at and say to my wife "this gets me around, but I'd like to make it better instead of repairing my junker car"

Should be simple, right?

Here's what I have so far. I have an 801 transaxle($40) that I rebuilt(~$40) and modified to have a much higher gear ratio. I have a 6.5hp push mower engine($10) that should run, but I haven't tinkered with yet. It's a Briggs quantum, so it should be good. I just picked up a Honda cb750 front and rear wheel, complete with drum brakes.($50) Although I'll only be using the front wheel for now.








Originally, I wanted to inspire my project on a Reliant Robin. Why? because I really liked the size and shape. However, I think my first build will be one seater. I really wanted a steering wheel, with a rack and pinion, but the larger wheel is pushing me more towards forks and handlebars for this build. The cb750 wheel is much bigger than I originally had in mind, but it will save me a bunch of time and money. Oh well, I'll see how it turns out as I go along.


I just finished rebuilding the transaxle. I cleaned out all the grease, and replaced it with gear oil. I replaced a few seized bearings and missing seals. I also modified one of the gears that goes to the differential. I did the same thing as this guy in the video:



This swaps the ratio of one of the gears from 0.43 to 2.32 going from the countershaft to the differential. This massively increases the output speed without increasing the input speed or the speed of the main or countershaft. Also, this transaxle has real ball bearings on the axles, so that's ideal too. The wheels are super rusted to the axles, so I'm not getting those off any time soon. So I'll have to stick with the current wheel base for now, no extensions.


I think that's about it for now. I'll have time to start putting things together this weekend. Oh, did I mention I'm building it out of wood? Of course not, that's a terrible idea! After all, wood is never used to build anything strong or critical like say, houses, or Rollercoasters. In reality, once you get over the initial shock, wood is an engineering material just like any other. It has it's advantages, like ease of fabrication. It has by far the lowest cost to strength ratio. But fear not. I'm going to be building something like this:



Or this:


Not this:


I've already fabbed up lots of steel braces and brackets out of angle iron with bolt holes. I've also bought some more too. Nothing structural is going to be be attached via wood screws, I promise you that.

All in all, I'm excited and optimistic. I will try my hardest not to get bored or hit an obstacle halfway through and forget about it for a year like some of my other projects.

Neat build, I like it when people do something creative with a build!
If you wanted a fourth wheel you could put it on, and if you get pulled over just say, “Oh, don’t mind that officer, that’s just the spare tire!”

This is fantastic! I was going to ask about a motorcycle front fork, but I see you are maybe headed that way. All of the design and parts necessary for a good front end are already there. 
Motorcycle tires on the back? If so, remember that they will automatically increase the speed, maybe that will help with not having to run the transaxle so fast. 
I’m concerned about the reliability of the transaxle though. Possibly it could be better supported than stock? I would keep an eye out for a small differential axle for future builds or replacement in this one. I’m scratching my head on that one to think of something. Not sure what is under a golf cart... 

Watching with great interest!

I'm not changing the rear wheels or tires. You can buy DOT quad tires for the rears. Now that I did the gearing change, my spreadsheet says I might actually have to put a bigger pulley on the transaxle than the engine, as the rear axle will now be spinning 5.4 times faster than stock with the same input shaft, main shaft, and counter shaft speeds. The speed increase is downstream of all these shafts, since it's applied to a jackshaft between the countershaft and the differential. It's really an ideal spot for the speed increase. The transaxle seems pretty solid as far as mounting goes. It's bolted to the frame an inch or so in from the outer axle ball bearings with 2x 5/16th bolts on each side, plus the front mounting points on the side.

Golf carts have a differential, but I had trouble finding cheap golf cart rear axles. There's a lot of golf courses around here and I have a feeling there are people buying up all the parts and broken carts. Peerless 100 differentials are impossible to find used as well.

Meanwhile I managed to make mounting brackets for the front axle. Luckily the drum brake mounts to the forks using a bolt and not a slot tab like some, so I don't have to fab up a bracket for the brake to push against. I've also got the transaxle pre-mounted to the two main beams. The transaxle wheels are at different distances, which is kind of annoying. Now that the transaxle is mounted to the beams, it's going to stay horizontal, so I was able to finally put gear oil in it without it leaking out the shifter shaft and the breather.

Something to bear in mind too is that some trucks used oak framed cabs until the mid 1950s. If you have Amish sawmills in your area, see about getting some larch. It's cheaper than box store lumber and it's about as weather resistant as pressure treated Southern Yellow Pine. That and it looks nicer IMHO.

Most cars and trucks were skinned with steel and had wooden innards until the 30s or later. LOTS of wood. It works fine.

Progress is much slower now that I can't work on it at work during lunch. Also I had some other stuff to do. I'm starting to get the frame put together. Putting together the forks is more effort than it should be. Made some very lovely axle brackets on the CNC and then split them with a bandsaw in a very ugly fashion.

I'm back. Had to take a break for a few months to work on some other more important stuff. So I changed my mind as far as, well, everything. I put the transaxle, mower engine, and the front wheel in the corner of the barn for a future build some day, and decided to instead convert my david bradley tractor that I got in a trade this summer with the original intention of making it go fast. I finally got it working reliably and had so much fun sitting on it driving it around the yard that I decided that it needed to be the basis of my mowercycle instead. Who doesn't love the sound of a big old briggs flathead, and pulling levers to actuate the clutch and change speed ratios?




So I pulled the transaxle off of it. since it's internally geared down 25:1, it would take significant effort to modify the internals. So I'm keeping the front wheels and axle, and putting the rear cb750 motorcycle wheel on the back. I want to keep the original friction plate clutch, and will initially try to use the lever operated cvt. However, I want to come back to that at a later time. By going this direction, I'm much closer to a rolling chassis. I just have to fabricate the rear part that hooks up to the motorcycle wheel.

The biggest hurdle is that the original transmission had a gear in it, so all the v belting going to it is spinning in the opposite direction from what I want it to. I think I am going to flip the engine around, and make a jack shaft to bring the power back across to the right side.

One issue I ran into was that the front axle pivots freely on a bolt. So I added some coil springs. This is just for now, I need to make this a little more solid and increase the spring preload. But it keeps the tractor from flopping over on its side for now. The springs are for a yard swing, with the little metal things taken out of the middle.



I fabbed up some brackets for the wheel using the CNC at work. I also welded together a mounting bracket that bolts up just like the old transmission did. Now I just have to connect the two.


This is what I have so far. Ignore the mess, it's winter so I barely have time to do fun stuff outside much less clean the barn.

OHHHHHHHH!!!!...Not sure how I feel about this build, but you seem to be coming along.  


Ignore me... I'm a David Bradley Suburban fan.

I’m watching. Kinda scary. I want to build one with a motorcycle FRONT end and 2 wheels in the back.

Cool beans man! In case you haven't figured out front brakes yet if you're going with 2 wheels on the front and a single in the rear... I came across this thread a few weeks ago and have been preparing the parts (which I already had) to do the same myself on my tractor build (spoiler alert!).

www.atltf.com/t4042-front-drum-brake-conversion-for-your-atlt

The motorcycle wheel already has a drum brake in it. For the front wheels, I might either machine a bracket so I can attach some moped disk brakes, or get some moped wheels with brakes on them already. I haven't confirmed the tire size on the front wheels, or really looked at them in general. If the hubs look sturdy, have good bearings, and I can find DOT tires for them I'll try to keep them.

Quote :

OHHHHHHHH!!!!...Not sure how I feel about this build, but you seem to be coming along.


Ignore me... I'm a David Bradley Suburban fan.

Well, it's missing the shroud, the transmission leaks, and isn't very useful to me as is. I'm trying to make as few permanent alterations to it as is reasonable. I really want to keep the original friction clutch mechanism, although I'll need to make a new shaft and mounting brackets, and maybe use a different linkage mechanism.

If I'm successful, it'll have a far better future than it ever would as a tractor.

A little bit of progress, we were all sick this weekend and it was super cold so I didn't feel like spending too much time outside.

The wheel is attached to the rest of the frame, and it stands up on its own!


I only have the bottom two frame members welded on so far, but it supports the weight of the tractor and me sitting on it! I even bounced on it a little. My welds must not be too bad then, especially since those pipes are only welded on the outside. I still have to remove the wheel and unbolt that bracket so I can get in and weld the inside parts. I'm using a harbor freight 110v flux core welder. However I made some modifications. I added a rectifier and a capacitor so that instead of it bieng AC it's now DC electrode negative, and that brought the weld quality up from garbage to quite nice. It's got just enough grunt to melt the half inch plate and the pipe.

I'm using 1/2in black steel pipe. It's cheap and thick, <$20 for 10 feet. I don't have a pipe bender and I couldn't get my really hot propane torch to work (barn was lousy with mud daubers this summer), so I bent the pipe by standing on it and hitting it with the welder until it got hot enough to bend. That seemed to work quite well.

The wheel is offset to the left from the center of the frame. The right side axle mounting plate is lined up with the right side of the frame bracket. This means the front sprocket will be in the middle of the frame C channel. There should be enough room. If the front sprocket ends up too small, I'll have to see if I can find a smaller rear sprocket, or change ratios elsewhere.

Here's a picture of the front tire. The tire size is 4.80/4.00-8. I might be able to get a DOT rated tire for this rim. The rim metal is very thick, so depending on how the bearings look and if they are easily replaceable, I'll likely use the rims and make a bracket for a disc brake to weld onto the rim.


All in all, I technically have a rolling chassis now, so that's nice.

Now it's actually rolling. Finished welding the rear frame piece, and it stands up on its own now. However, it's very wobbly and tippy, so the front suspension needs to be reworked before I can look at the drivetrain.

Looking good!

Since the engine is so tall, how about widening the front axle? You seem to have the skills to do that. It would only require stretching a few bits.

That's certainly possible. I'd need to find some square tubing that nicely slides over the axle tubing. If it feels tippy once I get it moving under its own power, I'll consider it. Should only have to make the axle and the steering rods longer.

I did a little bit of work on the front suspension this weekend. However I don't think it's going to work as-is. There's just no easy way to make it stay nicely centered. I can preload the springs a whole bunch, but that won't make it stay perfectly upright. The rigid pivoting axle isn't going to work.

I picked up these adorable little shocks for a song. They're rated for 750lbs each. I think I'm going to split the axle in half and have each side able to independently pivot. Then I'll put these shocks on so that they are fully extended when everything is nice and level. I'll set them with enough preload that the whole setup will be rigid most of the time, and only move when I hit a big bump or something. That should be a good midpoint between a rigid axle and something vastly more complex. I will likely also extend the axle so I have a longer wheelbase. I don't need very much suspension travel, so I'm not too worried about the toe-in changing when the suspension compresses.




However, before I do that, I want to work on the driveline. I removed the rear frame bracket and got some 3/4" pillow blocks and shaft. I want to remount the original friction clutch. However I'll need to remake the actuator as the original was quite broken and won't fit anyways. Hopefully I'll be able to work on this at work this week.

More progress! I've been working on the clutch during lunch at work this week, and it's starting to come together. I'm trying my best to use the original david bradley friction clutch because manual friction clutches are awesome. This clutch works with two v belt pulleys. The smaller outer one is pinned to the shaft, while the larger inner one has bushings that allow it to spin freely on the shaft. There is a friction disk between the two, and the drive belt from the engine goes on the inner pulley. The two pulleys are pushed together to engage the clutch and spin the jack shaft. The outer pulley is also part of the reverse, which I would like to try to implement at a later date.

The original clutch actuation method used a throw IN bearing that was moved by a lever. Well, not only was this custom bearing completely destroyed on my clutch, it also applied force to the bearing to engage the clutch. For a vehicle that will spend most of its time with the clutch engaged, you want the clutch to naturally be engaged, and the bearing applies force to disengage it.

First I had to drill two really big holes that were in line with each other. Luckily the drill press at work was just barely big enough to do it. Once I got the first pilot hole drilled, I had to put the long drill bit in the hole and then chuck it up. Once I got the pilot holes drilled, enlarging them with a step drill wasn't so bad.


Now I've got it a little bit together so that I can see that it will work. The spring pushes the two pulleys against each other. I will have to come up with a way to push on the other end of the shaft to disengage it. My biggest concern now is fitting the sprocket and chain in there around the mounting pipes. I may have to cut one of them and use a bolt on each side to attach it to the frame instead of long bolts going all the way across. Also, in order to be able to remove the shaft to work on it, I don't think I'll be able to weld the sprocket on the shaft. I may have to pin it or something, but I know some little set screws aren't going to handle the torque. I can cut a keyway in the shaft easy enough on the CNC, but I'd have to find a pre-slotted sprocket.

you reminded me that I need to get my big drill bits from my son’s shop. I think they call them Silver and Deming for some reason… half inch shanks up to about 1-1/4”. Very handy. A keyway broach is also handy, none at work?

Nah, it's a factory not a machine shop. Anything that needed keyways was already ordered with keyways.

Anyways, I got the clutch working on the bench. It's hydraulic, and I think I'll even be able to hook it to the original clutch lever! I ordered these random motorcycle hydraulics a long time ago for another project, so I had them laying around. I just had to find a hydraulic cable to hook them together, which was surprisingly hard. It seems to work well on the bench. I'm not a fan of how loose the hinge is on the throwout... thing, but it should work fine for now.

The only downside is that the front sprocket moves with the clutch shaft, but it shouldn't move enough to really mess up the chain. I'm ordering the chain this week, so I'll find out. The front sprocket I ordered has a keyway, so I cut a long one in the shaft as well. I don't know if I'll use the spring I have on there right now. I think I want a stiffer one. Oh, and I never checked to see if the pulley was sticking out the right amount, so I'll find out when I go to put it back on.

All in all, I think I'm almost ready to tackle flipping the engine around. That will be interesting as I'll have to figure out belt sizes and stuff. Beyond that, it's going to be little things like making a throttle pedal, and making a brake pedal and hooking at least the rear wheel brake up to it for initial testing. This is probably one of the biggest and longest running projects I've ever done.

Haven't done any work on it in a few weeks as my daughter was in the hospital with covid complications. Finally took the rear end home and got it mounted back on the frame yesterday. The wheel went on, the chain connected the wheel to the clutch shaft perfectly, everything looks pretty good.

However, the clutch spring is waaaay too weak. Also, the hydraulic cylinders might be too small. I'm going to need alot of force holding the clutch together, since it's going to be operating at the low speed high torque side of the drivetrain. I'm going to see if I can get some belleville disc springs. I need a lot of spring force, but I only need an eighth of an inch or so of travel to disengage it.

I might make my own hydraulic setup using some industrial air cylinders. That way I can cheaply get like an inch diameter cylinder to work. I've done it before on another project.

Work on this project might slow down a bit or take a break, as I got re-bit by the steam engine bug. But we will see how things go this summer, as there's not much left to buy for this project to get it moving, which is normally my main pace setter.

Hope your daughter is doing better and gets well quick.

rolphill wrote:

Now it's actually rolling. Finished welding the rear frame piece, and it stands up on its own now. However, it's very wobbly and tippy, so the front suspension needs to be reworked before I can look at the drivetrain.

looks like a extra dangerous version of a 3 wheeler. lol

Be cool to have stenciled in the hood “mowlaris” lol

I'm back to working on this. My ADHD makes me cycle through hobbies every few months. It's super annoying, but at least I am managing to spend longer on one hobby as I get older.

I pulled the mowercycle out of the shed. It was covered in spiderwebs and a little more rusty but still pretty much the same. I have an old motor-generator that I took apart and cleaned and now it works, so I put that on instead of the gas tank. I'll be relocating it somewhere else and using a vacuum powered fuel pump.

I also tried to flip the engine around. However, it doesn't fit well that way. For now I just left it off, and I'm going to weld up the front axle while I have better access to that area. I'm pretty sure this engine isn't the original. It sits on a steel plate, and it was bolted through the plate to the frame on one side, but it was just bolted to the plate on the other side. The plate wasn't welded to the frame or anything either. So it was only two bolts holding the engine to the frame. The information plate is long gone, but I bet this is probably like a 10 horsepower engine. It seems a bit bigger than the 8hp one I have in the barn.

So there's a bit of a problem. This engine is way too big and old. It needs a battery to power the coil, and it's size just doesn't match the shape of the rest of the vehicle. It's also going to be hard to route the jack shaft v belts around it with it flipped around. I'm thinking about trying to trade it for a new predator 212 or something similar. It's in pretty good shape. There's some leaky seals, but I managed to get it started this weekend without too much trouble. I'll think about it.